Conventionally, in embedded systems such as mobile terminals, real-time operating systems (OSs) have been adopted as OSs capable of real-time control. However, in recent years, the adoption of universal OSs, which have an advantage in terms of development costs, has been on the rise. Universal OSs do not perform real-time control and therefore, do not guarantee interrupt response.
As a technique of guaranteeing interrupt response, one approach monitors the time from interrupt notification until interrupt handler completion, and increases the processing priority level of threads for which the response is slow (for example, refer to Japanese Laid-Open Patent Publication No. S59-161738).
Nonetheless, with the conventional techniques above, if the load of the central processing unit (CPU) increases, the monitoring of the response time for interrupt processing is delayed, arising in a problem that real-time processing fails. Further, in the system, if a thread that has been set to have the highest priority level is delayed, the priority level cannot be further increased and real-time processing fails.